and prove that the pointwise limit in (REF ) exists at every \(x\in {{\mathbb {R}}^d}\) ,
and coincides with (REF ),
whenever \(f\in C^2({{\mathbb {R}}^d})\cap L_1(dy/(1+|y|)^N)\) , for some \(N>0\) ; see [1]},
and [2]}, [3]} for slightly less restrictive smoothness assumptions.
